<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<p>
     var i = i + 300;
</p>
<p>
     <code>
         var i = i + 300;
         alert('哈哈')
     </code>
</p>
</body>
</html>